THE MACKEKEL 181 



these lines, but it is stated that 171 large or ' first-class ' vessels 

 were fishing in the spring, and 771 in the autumn. 



The Irish statistics are interesting. They^ give 3,525 tons 

 as caught in the spring, and 6,146 tons in the autumn — a total 

 of 9,671 tons. But the total landed as given in Appendix No. 1 

 is 8,022 tons. The discrepancy of 1,650 tons or so is not 

 explained, but is no doubt explicable. 



Life-History 



Hjort 2 tells us that the natural history of mackerel ' has been 

 very little investigated, and very little material was obtained 

 during the cruise of the Michael Sars \ Allen and his colleagues 

 at Plymouth have shown that the fish spawns earlier in southern 

 waters than it does further north ; and Orton believes that it 

 probably breeds throughout its whole range only when the 

 water temperature at the surface is at least 53-6° to 55-4° F. 

 Off the British coast the spawning season starts in May and 

 lasts to the end of July. The mackerel shoals discharge their 

 eggs, about one-twentieth of an inch in diameter,^ near the 

 surface at a short distance from land ; the spent fish as they 

 spawn quit the shoals. Within forty- eight hours after fertiliza- 

 tion, as a rule, the eggs, although they are provided with an oil 

 globule, begin to sink ; they remain suspended at midwater for 

 a short time, and then sink to the bottom.'* At a temperature of 

 58° F. the period of incubation is about six days. The average 

 number of eggs produced by a female in America is about 

 40,000. But three fish at Woodshole have been known to give 

 an average of 144,833 eggs, and 546,000 have been taken from 

 a 1 J lb. fish. A large fish in Casco Bay has given 200,000 ; and 

 the largest of all are believed to yield probably as many as 

 a million. Within forty- eight hours of fertihzation the emlDryo 

 is visible in the egg. The xlmerican fish culturists, who hatch 

 out millions of eggs, find that, in hatching jars or hatching-boxes, 

 many eggs die at the end of the third day. In 1898 they 

 hatched, as a rule, less than one mackerel egg in a hundred, 

 though in some experiments they got results as good as 75 per 

 cent. By 1914 experience had taught them to hatch nearly 

 40 per cent., for 6 J million eggs produced 2 J million fry. Whether 

 eggs discharged in the sea are subject to like mortality is not 

 known, but it has been noticed that the eggs of mackerel which 

 have been a long time in the nets — as mackerel frequently are — 



1 Appendix 4 (a) and 5 (a). ^ Depths of Ocean. 



- The average diameter is 0047 inch, and therefore nearly 652,000 mackerel 

 eggs go to the quart. 

 ■ * Manual of Fish Cidture, pp. 212-13. 



